Span Filter (Sponge Filter): The Cheapest, Safest Filter for Fry, Bettas & Shrimp

A span filter (sponge filter) is a block of foam on a tube, powered by an air pump (pam udara). Air bubbles rise up the tube and pull water through the sponge, so dirt is trapped and good bacteria grow inside the foam. It's the cheapest and gentlest filter you can buy, it can't suck up fry or shrimp, and it adds oxygen at the same time. That's why Malaysian guppy, betta and shrimp breeders use rows of them. Use one medium sponge filter for a 1–2 kaki tank, two for a 3 kaki tank, and rinse it in old tank water, never tap water.

How a Sponge Filter Works

1. An air pump outside the tank pushes air through airline tubing.
2. The air enters the lift tube in the middle of the sponge, usually through a small airstone.
3. Rising bubbles create an upward current, which draws water in through the sponge and out the top of the tube.
4. The sponge traps debris (mechanical filtration) and hosts bacteria that convert ammonia and nitrite (biological filtration).

There's no motor in the water, no impeller and no intake slot, which is why it's so safe for small animals.

Types of sponge filters

Type	Description	Best for
Single sponge	One cylinder or block on a base	Betta tanks, fry tanks, 1 kaki tanks
Double sponge	Two sponges on one lift tube	2–3 kaki tanks, more capacity
Corner sponge	Triangle shape for tank corners	Nano and betta tanks
Wall-mount sponge	Sticks to the glass with suction cups	Shrimp tanks, space saving
Sponge on a powerhead	Uses a small water pump instead of air	More flow, but less gentle

You'll find sponges and replacement foam under Filter Accessories.

Why Breeders Use Span Filters

• Fry-safe and shrimp-safe: no intake can suck in babies.
• Gentle flow that long-finned bettas and fry can handle.
• Cheap to run: one air pump with a gang valve can power several tanks.
• Easy to move: a seeded sponge can go straight into a new or hospital tank so it starts with bacteria.
• Grazing surface: fry and shrimp pick at the biofilm on the foam.
• Medication-friendly: no carbon to remove meds, and sponges are easy to swap between tanks.

That's why you'll see them in guppy and betta breeding racks and fish farms across Johor and Perak.

Span Filter Sizing

Tank	Volume	Sponge filter	Air pump
Betta tub or small tank	5–15 L	1 small (nano)	Small single-outlet
1 kaki	12–15 L	1 small to medium	Single-outlet
1.5 kaki	~28 L	1 medium	Single-outlet
2 kaki	~55 L	1 large or 2 medium	Single or double outlet
3 kaki	~155 L	2 large	Double outlet or stronger pump
4 kaki and above	230 L+	Use as a secondary filter	Strong pump or air manifold

Sponge filters are best for lightly or moderately stocked tanks. For heavy feeders like goldfish or big fish, use them alongside a top filter or canister.

Sponge Filter With Air Pump: Setup

1. Rinse the new sponge in dechlorinated water to clear dust.
2. Attach airline tubing from the pump to the sponge filter's air inlet.
3. Add a check valve in the line so water can't siphon back into the pump during a power cut.
4. Place the pump above the water level, or keep the check valve fitted if it sits lower.
5. Use a control valve to set the bubble flow. For bettas and fry, a gentle stream is enough.
6. Seed the sponge: squeeze in some old filter mulm from an established tank, or add bottled bacteria. Read beneficial bacteria explained.

Air pumps and accessories are under Air Pumps, and our air pump guide explains outputs and noise.

How to Clean a Span Filter

The rule: clean it in tank water, not tap water. Chlorine in air paip kills the bacteria living in the foam.

1. During a water change, scoop some tank water into a bucket.
2. Lift the sponge out gently (put a cup under it so debris doesn't fall back).
3. Squeeze it in the bucket 3–5 times, until it releases most of the brown mulm.
4. Put it back and restart the air.

How often? When bubble flow slows down, or about every 2–4 weeks. Don't aim for a spotless sponge, because a little brown is healthy.

Replace the sponge only when it is crumbling or has lost its shape, and ideally run the old and new sponges together for a few weeks so bacteria transfer.

Power Cuts: Why Sponge Filters Are Resilient

TNB outages and tripped circuit breakers happen. Here's how a sponge filter compares:

• Gentle restart: when power returns, the air pump starts again with no priming, unlike some canisters that need re-priming.
• No dirty water flush: canisters that stand still can release stale water when they restart. Sponge filters don't trap water in a closed box.
• Battery backup is easy: a small battery-operated air pump can run a sponge filter during an outage, keeping oxygen and bacteria going.

Bacteria in any filter start to suffer after several hours without flow, so a battery air pump is a cheap insurance. Our guide to aquarium power outages covers more.

Sponge Filter for Betta

A sponge filter is one of the best choices for an ikan laga:

• The low flow doesn't push long fins around.
• It keeps the surface calm enough for bubble nests.
• It's quiet with a good air pump and a control valve.

Set it to a slow trickle of bubbles. See our betta care guide.

Pros and Cons

Pros	Cons
Cheapest filter to buy and run	Takes up space in the tank
Safe for fry, shrimp and bettas	Limited capacity for heavy stocking
Adds oxygen	Air pump can hum or bubble noisily
Easy to clean and move	Doesn't polish water as clear as canisters
Works well as a backup filter	Not a "hidden" look for display tanks

Frequently Asked Questions

Span filter perlu pam udara ke?

Ya, kebanyakan span filter perlu pam udara untuk berfungsi. Gelembung udara yang naik dalam tiub akan menarik air melalui span. Pilih pam udara ikut saiz akuarium dan letak injap sehala (check valve) supaya air tidak masuk ke dalam pam semasa elektrik terputus.

Macam mana nak cuci span filter?

Cuci span filter dalam air akuarium yang lama, bukan air paip. Picit span beberapa kali dalam baldi berisi air akuarium sehingga kotoran keluar, kemudian letak semula. Jangan cuci terlalu bersih kerana bakteria baik hidup dalam span.

Is a sponge filter enough for a 2 kaki tank?

For a lightly stocked community, betta or shrimp tank, yes, one large or two medium sponge filters work well. For goldfish or many fish, add a stronger filter too.

How long does a new sponge filter take to cycle?

Usually 3–6 weeks from scratch. Seeding with mulm from an established filter or bottled bacteria speeds it up.

Can I use a sponge filter for goldfish?

As a secondary filter, yes. Goldfish produce a lot of waste, so pair it with a top filter or canister.

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Build a simple, safe setup with sponge filters and filter accessories and air pumps from Malaysian sellers on FishyHub. Compare listings and RM prices, and ask the seller which pump suits your sponge size.